The present invention relates to a hangfire protection system and more particularly to an improved completely self-contained hangfire protection system for a gun having a relatively high rate of fire.
In many gun systems, the sequence is ramming, locking, firing, unlocking and extracting and feeding. In powered guns, such as those externally powered, the cycle continues even though the round has not fired. While this eliminates the possibility of gun stoppage due to a misfire, it does create a potentially hazardous situation.
Sometimes a round of ammunition does not fire properly, within the design limits of the ammunition, because of some unknown defect in the ammunition. Normally, a round fires within a prescribed time limit after the primer is struck, usually measured in milliseconds. When the primer of a round is struck, and the round fails to fire within the prescribed time limits, the round either fires late within an extended time limit, a hangfire, or does not fire at all and is a dud. Duds, which are not potentially dangerous, can be extracted and safely disposed of with relative ease.
A hangfire, on the contrary, presents a far more hazardous condition to the gun crew especially if the round is within the time limit which is greater than what experience or data has indicated to be the maximum interval within which the round normally fires.
For relatively high rate of fire weapons, powered through a repeating sequence, a hangfire can be quite dangerous since the lock-fire-unlock sequence is fairly short, and may be shorter than the maximum interval of hangfire. The result is that the round may be extracted while it is still possible for the round to go off with resulting personnel or gun damage, or both.
Hangfire should be distinquished from "cook-off", the latter a condition in which barrel or breech heat detonates the round without the primer being struck and which involves time periods substantially longer than those involved in hangfire. Cook-off is usually avoided by controlling normal gun shut-down so that the bolt is in the open bolt condition.